Laser pointer

ABSTRACT

A device to be used in combination with a surgical navigation system for defining the position of a straight line determined by an operating surgeon within a three-dimensional coordinate system in an operating theater. The devices includes a body ( 1 ) with a surface ( 2 ) and at least three markers ( 3 ) which emit waves ( 19 ) and the position of which can be determined within a three-dimensional coordinate system by a position detector belonging to the surgical navigation system. A laser ( 4 ) mounted on the body ( 1 ) emits a laser beam ( 5 ), directed away from the body ( 1 ), which has a geometrical central beam ( 6 ) and a wavelength in the visible range. The laser beam ( 5 ) is emitted in a geometrically defined position relative to the markers ( 3 ) so that the position of the central beam ( 6 ) relative to the three-dimensional coordinate system can be calculated from the previously measured positions of the markers ( 3 ) by a computer, which is also part of the surgical navigation system.

English translation of the International Patent Application No.PCT/CH00/00668 “Laser pointer” in the name of AO-EntwicklungsinstitutDavos

LASER POINTER

The invention relates to a device to be used in combination with asurgical navigation system for defining the position of a straight linedetermined by an operating surgeon within a three-dimensional coordinatesystem in an operating theatre as claimed in the precharacterising partof claim 1.

Increasingly, surgical navigation systems or devices known as ComputerAssisted Surgery Systems (CAS) are used for the treatment of bonefractures in surgical operation theatres. With the aid of imagingtechniques, these devices permit the utilisation of minimally invasivesurgical procedures by enabling a position measuring of surgicalinstruments and devices within a three-dimensional coordinate systemwhich is stationary relative to the operating theatre. This enables acomputer-controlled displacement and positioning of devices such asmedical robots or movable X-ray apparatuses, in particular those havingan X-ray source mounted on one end of a three-dimensionally movable,C-shaped bow and an X-ray receiver mounted on the other end thereof (inthe following briefly referred to as C-bow). A motor-driven andcomputer-controlled, movable C-bow of this type is disclosed in theinternational patent application PCT/CH00/00022.

Surgical navigation systems including a computer and a position detectorfor measuring the position of three-dimensionally movable, surgicalinstruments and devices are disclosed, for example, in U.S. Pat. No.5,383,454 BUCHOLZ and in EP 0,359,773 SCHLÖNDORFF. Surgical navigationsystems of this type are put on the market, for example, by the companyMEDIVISION, Oberdorf, Switzerland, under the trade name “Surgigate”. Inaddition to a computer provided with a data memory for storing X-rayphotographs or entire computer tomograms (CTs) taken and stored priorto, or during the operation for diagnostic purposes or for planning theintervention to be carried out, these systems comprise at least oneposition detector. Frequently, optoelectronic position detectors areused which are capable of measuring the positions of optical markersapplied to said surgical instruments or devices within athree-dimensional coordinate system in the operating theatre.Optoelectronic position detectors are commercially available, forexample, under the trade name Optotrak 3020 (manufactured by NorthernDigital, Ontario, Canada).

Usually, LEDs (light emitting diodes) or IREDs (infrared light-emittingdiodes) are used as optical markers, the positions of which within athree-dimensional coordinate system are detectable by the sensor of theposition detector, realised for example in the form of cameras or CCDs(charge-coupled devices).

Other position detectors may function on the basis of acoustic waves ormagnetic fields, instead of electromagnetic waves.

In order to define an image plane or an image normal to be occupied bythe C-bow, a pointer provided with markers, such as the one disclosed inU.S. Pat. No. 5,383,454 BUCHOLZ, may be positioned by the operatingsurgeon with its tip on the body of a patient while the shaft of thepointer is oriented in a selected direction corresponding to the imagenormal of the x-ray photograph to be taken. Pointers of this type arecommercially available, for example, under the trade name OptotrakDigitizing Probes (manufactured by Northern Digital, Ontario, Canada).The positions of the markers fixed to the pointer are measured by theposition detector and, based on these data, the position and orientationof the straight line defined by the longitudinal axis of the pointerwithin the three-dimensional coordinate system of the operating theatreis calculated by the computer. Subsequently, the C-bow may be displacedin a computer-controlled manner so as to occupy a position andprojection the image normal of which corresponds to the longitudinalaxis of the pointer. A disadvantage with the utilisation of suchpointers resides in the fact that they are relatively short, which makesit necessary for the operating surgeon to approach the patient veryclosely when working with the pointer. In addition, the position of theimage normal relative to the patient is not visualised with these knownpointers, so that only inaccurate predictions of the resultingprojection can be made. Due to the presence of the operating surgeon,the patient, and the C-bow, the visibility of the markers fixed on suchsmall-sized pointers may be strongly limited for the navigation systemand the markers may temporarily be even completely invisible.

The invention is intended to provide a remedy for this. It isaccordingly an object of the invention to create a pointer embodied insuch a way as to permit the operating surgeon to indicate the imagenormal or the projection plane from a greater distance. The greaterspatial distances between the operating surgeon, the patient, and thesurgical devices made possible by the invention permit an undisturbeddetection of the markers by the sensors of the position detector. Thusit is possible, for example, to position a computer-controlled,motor-driven C-bow close to the patient without running the risk of acollision between the operating surgeon and the C-bow.

According to the invention, this object is achieved by means of a deviceto be used in combination with a surgical navigation system which showsthe features of claim 1.

The inventive device to be used in combination with a surgicalnavigation system serves for defining the position of a straight linedetermined by the operating surgeon and of a plane extending verticallythereto within a three-dimensional coordinate system in an operatingtheatre. It comprises a body provided with at least three markers saidmarkers emitting waves. A laser is integrated into said body in such away that the laser beam, emitted concentrically to a central beam, isdirected away from the body. The wave length of the laser beam is in thevisible range, so that it is possible for the operating surgeon bydirecting the device and the laser beam adequately with respect to apatient to be treated so as to define a straight line in the operatingtheatre which intersects the patient and which corresponds, for example,to the image normal of a position and projection of a C-bow that is tobe adjusted. The laser is fixed within the body in a defined positionrelative to the markers, so that the direction of the central beam isdefined relative to the positions of the markers. The positions of themarkers are measured by a position detector which is part of thesurgical navigation system, so that the position of a straight linewithin a three-dimensional coordinate system in the operating theatremay be determined by means of a computer which is equally part of thesurgical navigation system and the C-bow may be displaced to the desiredposition and projection in a computer-controlled manner.

In one embodiment, the device according to the invention comprises ahandle which in the case of a battery-operated laser may be providedwith a cavity for receiving the batteries.

The wattage of the laser is in a range of between 2 mw and 1 W,preferably between 2 mw and 25 mw.

The waves emitted by the markers are either electromagnetic or acousticwaves, depending on the type of position detector used. If markersemitting electromagnetic waves are used, the following embodiments ofthe markers are envisageable:

-   -   LEDs (light-emitting diodes);    -   IREDs (infrared light-emitting diodes);    -   optical reflectors; or    -   a fibre-optic light guide charged by a light source.

If markers emitting acoustic waves are used, the markers are embodied asacoustic emitters.

In one embodiment of the device according to the invention, the body isshaped in the form of a prismatic or cylindrical rod provided with alongitudinal axis. Preferably, the laser is integrated in the rod insuch a way that the central beam coincides with the longitudinal axis ofthe rod and that the emitted laser beam is directed away from one of therod ends. Three markers may be fixed in a non-collinear way to the rodor may be arranged on a straight line, preferably on the longitudinalaxis, the three markers being arranged, in the latter case, at distances(A) or (B), respectively, relative to one another, with (A) beingunequal to (B), so that it is possible to determine the direction ofemission of the laser beam.

In another embodiment of the device according to the invention, the bodyis realised in the form of a planar plate, the markers being preferablyarranged in a non-collinear way and emitting waves directed away fromthe surface of the plate. The laser is inserted substantially on centrein the plate, so that the laser beam emitted is directed away from thebottom surface of the plate.

Preferably, the markers are arranged in a plane extending parallel tothe top surface, said plane and said top surface being likely tocoincide and the laser beam is emitted vertically to said plane.

In a further embodiment of the device according to the invention, thelaser comprises a system of lenses adapted to the wave length of thelaser beam in order to allow the laser beam to be emitted in ageometrically defined position and direction relative to the positionsof the markers. Instead of the system of lenses, a fibre-opticappliance, a system of optical reflectors or any other suitable beamdeflection system may be used.

Further advantageous embodiments of the invention will be characterisedin the dependent claims.

The advantages achieved by the present invention consist essentially inthe fact that the device according to the invention makes it possible todefine a straight line and a plane extending vertically thereto,relative to a patient in the operating theatre, which serves as a simplevisualisation means for the computer-controlled positioning of a medicalapparatus, such as the adjustment of the position and projection of aC-bow. Due to the reach of the laser beam, the operating surgeon mayfreely move in the operating theatre when indicating the straight lineby means of the inventive device, so that it is possible, for example,to position the C-bow without getting in the way of the operatingsurgeon.

In the following, the invention and improvements of the invention willbe illustrated in greater detail with reference to the partiallydiagrammatic representations of several embodiments.

IN THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of the device accordingto the invention; and

FIG. 2 is a side view of another embodiment of the device according tothe invention.

FIG. 1 shows an embodiment of the device according to the inventionhaving a body 1 which is shaped in the form of a planar, triangularplate with a top surface 11 and a bottom surface 12, and a laser 4 whichis arranged on centre relative to the ground plan of the plate and emitsthe laser beam 5 away from the bottom surface 12 into the operatingtheatre. The emitted laser beam 5 has a wave length in the visible rangeand a geometrical central axis 6. In order to allow the laser beam 5 tobe emitted in a geometrically defined position and direction in relationto the markers 3, the laser 4 comprises means 20, preferably realisablein the form of a system of lenses, which are arranged in the area of thebottom surface 12 on the front portion of the laser 4. The body 1 isequally provided with three markers 3 embodied as LEDs placed each inone of the corners of the ground plan of the plate in such a way thatthe waves 19 embodied in the form of electromagnetic waves are emittedaway from the top surface 11 into the operating theatre. A handle 8 isfixed on the side of the plate by means of which the body 1 is manuallyfreely movable. The handle 8 comprises a cavity 10 wherein two batteries9 serving as a source of energy for the laser 4 are accommodated. Thepower supply of the laser 4 is realised via a cable 14 which leads fromthe batteries 9 to the laser 4 and is integrated into the body 1. Itwould also be possible to pass the cable 14 on the outside of the body1, either along the bottom surface 12 or along the top surface 11. Thecables 13, which assure the power supply of the markers 3, areintegrated into the body 1 on part of their lengths. The markers 3,embodied as LEDs, are supplied in a centralised way by the navigationsystem. For this purpose, the markers 3 embodied as LEDs are controlledin pulsed mode by the navigation system. The temporal correlationbetween the control pulses and the lighting up of the individual markers3 enables the positional detection by the navigation system of thesurgical instruments provided with markers 3 in the operating theatre.

The embodiment of the inventive device shown in FIG. 2 differs from theembodiment shown in FIG. 1 only in so far as the body 1 is shaped in theform of a cylindrical or prismatic rod 15. The rod 15 has a central axis16, a front end portion 18, and a rear end portion 17. The laser 4 isintegrated into the rod 15 and extends coaxially to the central axis 16.The means 20 permitting the laser beam 5 to be emitted in ageometrically defined position and direction relative to the markers 3,which as in the above example are preferably realised in the form of asystem of lenses, are arranged on the front portion of the laser 4 andextend in the direction of the front end portion 18, so that thegeometrical central beam 6 of the laser beam 5 coincides with thecentral axis 16. The handle 8 with the cavity 10 for receiving twobatteries 9 assuring the power supply of the laser 4 is arranged on therod 15 at a right angle to the central axis 16. The power supply of thelaser 4 is realised via the cable 14 which is integrated into the rod 15and connects the laser 4 to the batteries 9. Three markers 3, embodied,as in the above example, in the form of LEDs, are arranged on a straightline coinciding with the central axis 16, one marker 3 being arrangedclose to the front end portion 18, another marker 3 close to the rearend portion 17, and the third marker 3 being located in an intermediateposition on the rod 15. The intermediate marker 3 and the marker 3arranged close to the rear end portion 17 are separated by a distance A,whereas the intermediate marker 3 and the marker 3 arranged close to thefront end portion 18 are separated by a distance B. The distances A andB are of unequal length (A<B) so as to make it possible to determine thedirection of emission of the laser beam 5 from the measurement of thepositions of the markers 3 by the navigation system. As in the aboveexample, the cables 13, which assure the power supply of the markers 3,are integrated into the body 1 on part of their lengths and lead awayfrom the handle 8 towards the navigation system.

1. A device to be used in combination with a surgical navigation systemfor defining the position of a straight line determined by an operatingsurgeon within a three-dimensional coordinate system in an operatingtheatre, including: A) a body (1) having a surface (2) and at leastthree markers (3) emitting waves (19), positions of said markers beingdetermined within the three-dimensional coordinate system by means of aposition detector that is part of the surgical navigation system;whereby B) the body (1) comprises a laser (4) that emits a laser beam(5), directed away from the body (1), said laser beam having ageometrical central beam (6) and a wavelength in the visible range; andC) a position of the central beam (6) relative to the three-dimensionalcoordinate system may be calculated from the determined positions of themarkers (3) by means of a computer that is also part of the surgicalnavigation system; and wherein D) the body (1) is a planar plate with atop surface (11) and a bottom surface (12); E) the laser beam (5) isemitted so as to be directed away from the bottom surface (12); and F)the markers (3) are arranged in a plane extending parallel to the topsurface (11) and the laser beam (5) is emitted vertically relative tosaid plane.
 2. The device as claimed in claim 1, wherein the laser (4)comprises means (20) permitting the laser beam (5) to be emitted in ageometrically defined position and direction relative to the markers(3).
 3. The device as claimed in claim 2, wherein said means (20)comprise a system of lenses adapted to the wavelength of the laser beam(5).
 4. The device as claimed in claim 2, wherein the means (20)comprise a fiber-optic appliance permitting the laser beam (5) to beemitted in a geometrically defined position and direction relative tothe markers (3).
 5. The device as claimed in claim 1, wherein the body(1) comprises a handle (8).
 6. The device as claimed in claim 1, whereinthe laser (4) may be operated by at least one battery (9).
 7. The deviceas claimed in claim 6, wherein the body (1) comprises a handle (8) andthe handle (8) comprises a cavity (10) into which the at least onebattery (9) is insertable.
 8. The device as claimed in claim 1, whereinthe laser (4) has a power range of between 2 mw and 1W.
 9. The device asclaimed in claim 8, wherein the laser power is between 2 mw and 25 mw.10. The device as claimed in claim 1, wherein the waves (19) areelectromagnetic waves.
 11. The device as claimed in claim 10, whereinthe markers (3) are light emitting diodes.
 12. The device as claimed inclaim 10, wherein the markers (3) are infrared light-emitting diodes.13. The device as claimed in claim 10, wherein the markers (3) areoptical reflectors.
 14. The device as claimed in claim 10, wherein themarkers (3) are fiber-optic light guides charged by a light source. 15.The device as claimed in claim 1, wherein the waves (19) are acousticwaves.
 16. The device as claimed in claim 15, wherein the markers (3)are acoustic emitters.
 17. The device as claimed in claim 1, wherein thebody (1) is a planar plate having a longitudinal axis (16), a front endportion (18), and a rear end portion (17), and wherein the laser (4) isintegrated into the planar plate so that the laser beam (5A) is emittedcoaxially to the central axis (16) and directed away from either one ofsaid front and rear end portions (17; 18).
 18. The device as claimed inclaim 1, wherein the at least three markers (3) are arranged on astraight line, a first two of said at least three markers (3) beingseparated from each other by a distance (A) and a second two of said atleast three markers (3) being separated by a distance (B), the distances(A) and (B) being unequal.
 19. The device as claimed in claim 18,wherein the straight line coincides with the central beam (6).
 20. Thedevice as claimed in claim 1, wherein, said at least three markers (3)are arranged in a non-collinear manner and emit waves from the body topsurface (11), and the laser (4) is inserted substantially on center inthe plate.
 21. The device as claimed in claim 20, wherein said plane isformed by the top surface.